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Other Causes of Flooding

Dams and dam failures can also lead to flooding. One of the most‐deadly events occurred in Italy. In 1960, the Vajont Dam was constructed, and it was one of the tallest dams in the world. Unfortunately, when the dam was filled up this caused the neighboring mountainside to become water‐logged. Although the dam was drained 1/3 the capacity, a massive mudslide created a wave that overtopped the dam. 50 million cubic meters of water rushed down into the Piave Valley below, and 1,900–2,500 people lost their lives in this disaster.

In the United States, a flash flood occurred in Idaho on June 5, 1976. The Teton Dam suffered a catastrophic failure. The rushing water killed 11 people and over 13,000 cattle. In 2017, the Oroville Dam in California almost collapsed and forced the evacuation of nearly 200,000 people. The repairs cost over $1 billion. Sadly, many of the dams in the United States are aging and even reaching the end of their lifespan. In fact, in a recent assessment, 91,000 dams in the United States received a D‐letter grade. There is concern that more episodes of flooding will result.

Storm surges and coastal erosion may result from hurricanes or other types of phenomena in the hydrosphere (e.g., low‐pressure systems, strong winds, high tides, etc.). A storm surge is a temporary rise in the water level of an ocean or river estuary. Flooding is a product of storm surges, and it can take days and weeks for water to recede after such events. Coastal erosion may also occur as a result of storm surges, and it often damages roads, bridges, dunes and beaches. Louisiana and Florida are frequently affected by storm surges and coastal erosion associated with hurricanes. Losses can amount to millions of dollars.

Droughts are another kind of hazard related to the hydrologic system. Low amounts of rainfall and high evaporation rates due to warm or hot temperatures lead to conditions of drought. Dust storms, desertification, and salinization of soil also result from droughts. Drought can have a negative impact on agricultural output. The Great Depression was triggered, in part, by severe drought. However, droughts do not typically result in a substantial shortage of the overall food supply in the United States (although the provision of individual crops may be extremely low). In contrast, famines in other countries can be especially deadly. The lack of adequate food intake has resulted in malnourishment and the spread of fatal diseases in Ethiopia in the 1980s and Niger in the mid‐2000s.